Multi-trp codebook

ABSTRACT

Embodiments of the present disclosure provide a method, a device and a computer readable medium for communication based on a multi-TRP codebook. According to a method for communication, a terminal device measures downlink channel conditions related to a plurality of network devices in communication with the terminal device. The terminal device selects a precoding matrix from a codebook based on the downlink channel conditions, elements in a column of the codebook represent respective beam sets for the plurality of network devices, and the precoding matrix indicates respective beams for the plurality of network devices. The terminal device transmits an index of the precoding matrix to at least one of the plurality of network devices. The embodiments of the present disclosure enable multi-TRP PMI feedback based on the proposed multi-TRP codebook.

FIELD

Embodiments of the present disclosure generally relate to wirelesscommunication, and in particular, to a method, a device and a computerreadable medium for communication based on a multi-TRP codebook.

BACKGROUND

The latest developments of the 3GPP standards are referred to as LongTerm Evolution (LTE) of Evolved Packet Core (EPC) network and EvolvedUMTS Terrestrial Radio Access Network (E-UTRAN), also commonly termed as‘4G’. In addition, the term ‘5G New Radio (NR)’ refers to an evolvingcommunication technology that is expected to support a variety ofapplications and services. 5G NR is part of a continuous mobilebroadband evolution promulgated by Third Generation Partnership Project(3GPP) to meet new requirements associated with latency, reliability,security, scalability (e.g., with Internet of Things (IoT)), and otherrequirements. Some aspects of 5G NR may be based on the 4G Long TermEvolution (LTE) standard.

Recently, the study of NR system was approved. The NR will considerfrequency ranges up to 100 GHz with the objective of a single technicalframework addressing all defined usage scenarios, requirements anddeployment scenarios, including enhanced mobile broadband, massivemachine-type-communications, and ultra-reliable and low latencycommunications. Discussion of multi-antenna scheme for new radio accesshas been started, including multi-antenna scheme, beam management,channel state information (CSI) acquisition, and reference signal andquasi co-located (QCL). Also, single-TRP transmission and multi-TRPtransmission have been agreed in NR. However, multi-TRP/paneltransmission is down-prioritized in current study, and will be discussedin future developments.

SUMMARY

In general, example embodiments of the present disclosure provide amethod, a device and a computer readable medium for communication basedon a multi-TRP codebook.

In a first aspect, there is provided a method for communication. Themethod comprises measuring downlink channel conditions related to aplurality of network devices in communication with a terminal device.The method also comprises selecting a precoding matrix from a codebookbased on the downlink channel conditions, elements in a column of thecodebook representing respective beam sets for the plurality of networkdevices, the precoding matrix indicating respective beams for theplurality of network devices. The method further comprises transmittingan index of the precoding matrix to at least one of the plurality ofnetwork devices.

In a second aspect, there is provided a terminal device. The terminaldevice comprises a processor and a memory storing instructions. Thememory and the instructions are configured, with the processor, to causethe terminal device to measure downlink channel conditions related to aplurality of network devices in communication with a terminal device.The memory and the instructions are also configured, with the processor,to cause the terminal device to select a precoding matrix from acodebook based on the downlink channel conditions, elements in a columnof the codebook representing respective beam sets for the plurality ofnetwork devices, the precoding matrix indicating respective beams forthe plurality of network devices. The memory and the instructions arefurther configured, with the processor, to cause the terminal device totransmit an index of the precoding matrix to at least one of theplurality of network devices.

In a third aspect, there is provided a computer readable medium havinginstructions stored thereon. The instructions, when executed on at leastone processor of a device, cause the device to carry out the methodaccording to the first aspect.

It is to be understood that the summary section is not intended toidentify key or essential features of embodiments of the presentdisclosure, nor is it intended to be used to limit the scope of thepresent disclosure. Other features of the present disclosure will becomeeasily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some embodiments of the presentdisclosure in the accompanying drawings, the above and other objects,features and advantages of the present disclosure will become moreapparent, wherein:

FIG. 1 is a block diagram of a communication environment in whichembodiments of the present disclosure can be implemented;

FIG. 2 shows a flowchart of an example method in accordance with someembodiments of the present disclosure; and

FIG. 3 is a simplified block diagram of a device that is suitable forimplementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numeralsrepresent the same or similar elements.

DETAILED DESCRIPTION OF EMBODIMENTS

Principle of the present disclosure will now be described with referenceto some example embodiments. It is to be understood that theseembodiments are described only for the purpose of illustration and helpthose skilled in the art to understand and implement the presentdisclosure, without suggesting any limitations as to the scope of thedisclosure. The disclosure described herein can be implemented invarious manners other than the ones described below.

In the following description and claims, unless defined otherwise, alltechnical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skills in the art to which thisdisclosure belongs.

As used herein, the term “transmission/reception point” may generallyindicate a station communicating with the user equipment. However, thetransmission/reception point may be referred to as different terms suchas a base station (BS), a cell, a Node-B, an evolved Node-B (eNB), anext generation NodeB (gNB), a Transmission Reception Point (TRP), asector, a site, a base transceiver system (BTS), an access point (AP), arelay node (RN), a remote radio head (RRH), a radio unit (RU), anantenna, and the like.

That is, in the context of the present disclosure, thetransmission/reception point, the base station (BS), or the cell may beconstrued as an inclusive concept indicating a portion of an area or afunction covered by a base station controller (BSC) in code divisionmultiple access (CDMA), a Node-B in WCDMA, an eNB or a sector (a site)in LTE, a gNB or a TRP in NR, and the like. Accordingly, a concept ofthe transmission/reception point, the base station (BS), and/or the cellmay include a variety of coverage areas such as a megacell, a macrocell,a microcell, a picocell, a femtocell, and the like. Furthermore, suchconcept may include a communication range of the relay node (RN), theremote radio head (RRH), or the radio unit (RU).

In the context of the present disclosure, the user equipment and thetransmission/reception point may be two transmission/reception subjects,having an inclusive meaning, which are used to embody the technology andthe technical concept disclosed herein, and may not be limited to aspecific term or word. Furthermore, the user equipment and thetransmission/reception point may be uplink or downlinktransmission/reception subjects, having an inclusive meaning, which areused to embody the technology and the technical concept disclosed inconnection with the present embodiment, and may not be limited to aspecific term or word. Herein, an uplink (UL) transmission/reception isa scheme in which data is transmitted from user equipment to a basestation. Alternatively, a downlink (DL) transmission/reception is ascheme in which data is transmitted from the base station to the userequipment.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The term “includes” and its variants are to be read as openterms that mean “includes, but is not limited to.” The term “based on”is to be read as “based at least in part on.” The term “one embodiment”and “an embodiment” are to be read as “at least one embodiment.” Theterm “another embodiment” is to be read as “at least one otherembodiment.” The terms “first,” “second,” and the like may refer todifferent or same objects. Other definitions, explicit and implicit, maybe included below.

In some examples, values, procedures, or apparatus are referred to as“best,” “lowest,” “highest,” “minimum,” “maximum,” or the like. It willbe appreciated that such descriptions are intended to indicate that aselection among many used functional alternatives can be made, and suchselections need not be better, smaller, higher, or otherwise preferableto other selections.

FIG. 1 is a block diagram of a communication environment 100 in whichembodiments of the present disclosure can be implemented. In thecommunication environment 100, there are two network devices 110, 120and a terminal device 130. The terminal device 130 may communicate withone or both of the network devices 110, 120 via wireless communicationlinks. It is to be understood that the number of network devices and thenumber of terminal devices are only for the purpose of illustrationwithout suggesting any limitations. The communication environment 100may include any suitable number of network devices and terminal devicesadapted for implementing embodiments of the present disclosure.

As used herein, the term “network device” or “base station” (BS) refersto a device which is capable of providing or hosting a cell or coveragewhere terminal devices can communicate. Examples of a network deviceinclude, but not limited to, a Node B (NodeB or NB), an Evolved NodeB(eNodeB or eNB), a next generation NodeB (gNB), a Transmission/ReceptionPoint (TRP), a Remote Radio Unit (RRU), a radio head (RH), a remoteradio head (RRH), a low power node such as a femto node, a pico node,and the like.

As used herein, the term “terminal device” refers to any device havingwireless or wired communication capabilities. Examples of the terminaldevice include, but not limited to, user equipment (UE), personalcomputers, desktops, mobile phones, cellular phones, smart phones,personal digital assistants (PDAs), portable computers, image capturedevices such as digital cameras, gaming devices, music storage andplayback appliances, or Internet appliances enabling wireless or wiredInternet access and browsing and the like. For the purpose ofdiscussion, in the following, some embodiments will be described withreference to UEs as examples of terminal devices and the terms “terminaldevice” and “user equipment” (UE) may be used interchangeably in thecontext of the present disclosure.

The communications in the communication environment 100 may conform toany suitable standards including, but not limited to, Global System forMobile Communications (GSM), Extended Coverage Global System for MobileInternet of Things (EC-GSM-IoT), Long Term Evolution (LTE),LTE-Evolution, LTE-Advanced (LTE-A), Wideband Code Division MultipleAccess (WCDMA), Code Division Multiple Access (CDMA), GSM EDGE RadioAccess Network (GERAN), and the like. Furthermore, the communicationsmay be performed according to any generation communication protocolseither currently known or to be developed in the future. Examples of thecommunication protocols include, but not limited to, the firstgeneration (1G), the second generation (2G), 2.5G, 2.75G, the thirdgeneration (3G), the fourth generation (4G), 4.5G, the fifth generation(5G) communication protocols.

As mentioned above, the terminal device 130 may communicate with one orboth of the network devices 110, 120 via transmissions on the forwardand reverse links. As used herein, the forward link (or downlink) refersto the communication link from the access networks to the terminals, andthe reverse link (or uplink) refers to the communication link from theterminals to the access networks. These communication links may beestablished via a single-in-single-out, multiple-in-signal-out or amultiple-in-multiple-out (MIMO) system.

A MIMO system employs multiple transmit antennas and multiple receiveantennas for data transmission. A MIMO channel formed by the transmitand receive antennas may be decomposed into a plurality of independentchannels, which are also referred to as spatial channels. Each of theseindependent channels corresponds to a spatial dimension. The MIMO systemcan provide improved performance (e.g., higher peak rates and/orcoverage) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

One of the MIMO technologies that have been used in cellular systems isclosed loop transmit precoding. In communication environment 100, it isassumed that the network devices 110, 120 and the terminal device 130support the closed loop transmit precoding. The network devices 110, 120can switch among their respective beams to adapt changes in conditionscaused by movement of the terminal device 130, or variation inenvironmental conditions within a cell.

For example, the network device 110 may use one or more of its fourbeams 112, 114, 116, and 118 to communicate with the terminal device130. Analogously, the network device 120 may use one or more of its fourbeams 122, 124, 126, and 128 to communicate with the terminal device130. This process may also be referred to as beamforming. It is to beunderstood that the particular number of beams for network devices 110,120 is only for the purpose of illustration without suggesting anylimitations. The network devices 110, 120 may have any same or differentnumbers of beams in other embodiments.

Taking the network device 110 as an example, when performingbeamforming, channel state information (CSI) is obtained at the networkdevice 110 and is used to precode data before being modulated andtransmitted from antennas of the network device 110. The network device110 transmits downlink (DL) reference signal(s) from its designatedantenna ports which are used by the terminal device 130 to calculateCSI. The CSI is then encoded and fed back to the network device 110using either an UL control channel or by multiplexing on an UL datachannel. At the network device 110, the received feedback CSIinformation is decoded and used to calculate precoding information. Thisprecoding information is then applied to the DL data channel beforetransmission from the antenna ports.

In codebook-based implicit feedback schemes, the terminal device 130 andthe network device 110 generally use a common or shared codebook. Theterminal device 130 would ideally search over the shared codebook on allpossible ranks and associated precoding matrices for each rank, thatbest represents the channel based upon the reference signal measurement,or that gives the maximum received signal. Then the terminal device 130feeds back the selected rank as a rank indicator (RI) and the index ofthe selected precoding matrix within the codebook of the selected rank,referred to as a precoding matrix index (PMI).

At the network device 110, the RI and the PMI are used to select theprecoding matrix from the shared codebook. The network device 110 willthen use CQI and the obtained PMI, possibly along with other feedbackinformation (for example HARQ) and other measurements to decide thetransmit precoding to use for the incoming DL data transmission. In theexample scenario of FIG. 1, it is assumed that each transmission beam112-118 corresponds to a different precoding matrix.

In 5G wireless communications, massive MIMO is one of the key enablingtechnologies. A large number of antenna elements bring extra degrees offreedom for increasing the throughput and considerable beamforming gainsfor improving the coverage. In practice, a large number of antennaelements can be assembled into multiple antenna panels for the purposeof cost reduction and power saving. Currently, the 3GPP specificationsdefine the codebook represents a same beam for different panels of anetwork device, a column of the codebook may be written as below.

$W_{l,m,p,n} = \begin{bmatrix}v_{l,m} \\{\varphi_{n0}v_{l,m}} \\{a_{p1}b_{n1}v_{l,m}} \\{a_{p2}b_{n2}v_{l,m}}\end{bmatrix}$

where the quantity v_(l,m) is a vector related to a beam set, theparameter combination (l, m) may be regarded as an index of the beam,and the quantities φ_(n0), a_(p1), a_(p2), b_(n1), b_(n2) are variousparameters for control of the beam set. More details for the codebookcan be found in 3GPP Release 15 specifications.

In this column of the conventional codebook, the upper two elementsv_(l,m) and φ_(n0)v_(l,m) represent one panel of a network device, andthe lower two elements a_(p1)b_(n1)v_(l,m) and a_(p2)b_(n2)v_(1an)represent another panel of the network device. This means that the twopanels of the network device use the same beam (l, m). The reason isthat the two panels of the same network device have the samegeographical location, and thus the optimal beams from the two panelsfor communicating with a same terminal device are identical.

However, in the communication scenario as depicted in FIG. 1 where theterminal device 130 may be in communication with two network devices110, 120, beams for different panels/antenna groups in different TRPsare usually different. For example, the beam 116 of the network device110 is an optimal beam for communication with the terminal device 130,whereas the beam 124 of the network device 120 is an optimal beam forcommunication with the terminal device 130. That is, for differentnetwork devices 110, 120, the optimal beams for communication with theterminal device 130 are different. In this event, the traditionalcodebook may be not suitable for the terminal device 130 to feed back todifferent network devices 110, 120.

In other words, the conventional codebook design is only for singleTRP/panel, while for multi-TRP transmission, if PMI feedback is based oncodebook, the current 3GPP specification is not sufficient to supportmultiple TRPs. Embodiments of the present disclosure provide method andapparatus to design a common framework for initial access of both singleand multiple beam based deployments. Particularly, new codebook designis proposed to support a plurality of TRPs, with different beam indicesfor different TRPs/panels. Also, new codebook design is proposed tosupport dynamic feedback for a single TRP and multiple TRPs. With theembodiments of the present disclosure, multi-TRP PMI feedback may bebased on the proposed multi-TRP codebook. In the following, the proposedmulti-TRP codebook and a method for communication based on the proposedmulti-TRP codebook will be detailed with reference to FIG. 2.

FIG. 2 shows a flowchart of an example method 200 in accordance withsome embodiments of the present disclosure. The method 200 can beimplemented at the terminal device 130 as shown in FIG. 1. It is to beunderstood that the method 200 may include additional blocks not shownand/or may omit some blocks as shown, and the scope of the presentdisclosure is not limited in this regard.

For the purpose of discussion, the method 200 will be described from theperspective of the terminal device 130 with reference to FIG. 1.Moreover, although the following description may be based on the factthat the terminal device 130 is in communication with two networkdevices 110, 120, all the embodiments described herein are alsoapplicable to communication scenarios where the terminal device 130 isin communication with three or more network devices.

At block 210, the terminal device 130 measures downlink channelconditions related to a plurality of network devices in communicationwith the terminal device 130, for example the network devices 110, 120.In some embodiments, the network devices 110, 120 may be two gNBs whichcollectively serve the terminal device 130 and have communication witheach other. In other embodiments, the network devices 110, 120 may betwo remote antennas of a same gNB (for example, two TRPs), which arelocated at different geographical locations. Because the network devices110, 120 may be located at different geographical locations, thedownlink channel conditions related to the network devices 110, 120 mayalso be different.

As an example, for performing the measurements, the terminal device 130may detect downlink reference signals transmitted by the network devices110, 120. The downlink channel conditions related to the network devices110, 120 may be then determined from the detection of the downlinkreference signals, such as the receiving quality of the signals. It isto be understood that the embodiments of the present disclosure are notlimited to using downlink reference signals, and other suitable ways tomeasure the downlink channel conditions related to the network devices110, 120 may also be possible.

At block 220, the terminal device 130 selects a precoding matrix from acodebook based on the downlink channel conditions. As discussed above,the proposed multi-TRP codebook may include beam information for aplurality of network devices in communication with the terminal device130, such as network devices 110, 120. To this end, elements in a columnof the proposed multi-TRP codebook represent respective beam sets forthe plurality of network devices, such as network devices 110, 120. Withthis codebook design, the precoding matrix selected from the proposedmulti-TRP codebook indicates respective beams for the plurality ofnetwork devices, such as network devices 110, 120.

In some embodiments, a terminal device may be configured with differentparameters for different scenarios, for example, a terminal device maybe configured with different codebooks or codebook types forsingle-TRP/panel transmission or multi-TRP/panel transmission. Forexample, based on the configured codebook or codebook type, a terminaldevice will select rank indicator and/or precoding matrix indicatoramong different sets of codebooks.

In some embodiments, a column of the multi-TRP/panel codebook may bewritten as below.

$W_{l,m,l^{\prime},m^{\prime}} = {{\begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{\beta \cdot v_{l^{\prime},m^{\prime}}} \\{\gamma \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}\mspace{14mu}{or}\mspace{14mu} W_{l,m,l^{\prime},m^{\prime}}} = {{\begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{\beta \cdot v_{l^{\prime},m^{\prime}}} \\{\gamma \cdot v_{l^{\prime},m^{\prime}}} \\{\theta \cdot v_{l,m}} \\{\delta \cdot v_{l,m}} \\{\mu \cdot v_{l^{\prime},m^{\prime}}} \\{\omega \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}\mspace{14mu}{or}\mspace{14mu} W_{l,m,l^{\prime},m^{\prime}}} = \begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{\beta \cdot v_{l,m}} \\{\gamma \cdot v_{l,m}} \\{\theta \cdot v_{l^{\prime},m^{\prime}}} \\{\delta \cdot v_{l^{\prime},m^{\prime}}} \\{\mu \cdot v_{l^{\prime},m^{\prime}}} \\{\omega \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}}}$

where the quantity v_(l,m) is a vector related to a first beam set, andthe quantity v_(l′,m′) is a vector related to a second beam set, theparameter combination (l, m) and (l′, m′) may be regarded as indices oftwo different beams, respectively. For example, the parametercombination (l, m) and (l′, m′) may be selected independently.

In some embodiments, the quantities α, β, γ, θ, δ, μ, ω are variousparameters for control of the beam sets, for example, the quantities α,β, γ, θ, δ, μ, ω may be phase rotation between beam sets. In someembodiments, both of the values of parameter combination (l, m) and (l′,m′) should be reported from a terminal device to a network device. Forexample, the values can be jointly encoded or separately encoded. Insome embodiments, for the single codebook, there may be twoconfigurations of codebook subset restriction (CBSR). For example, oneCBSR is used for restriction of (l, m) and the other CBSR is used forrestriction of (l′, m′).

In some embodiments, a column of the multi-TRP/panel codebook may bewritten as below.

$W_{l,m,l^{\prime},m^{\prime},{l^{''}m^{''}},{l^{\prime}}^{''},{m^{\prime}}^{''}} = \begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{\beta \cdot v_{l^{\prime},m^{\prime}}} \\{\gamma \cdot v_{l^{\prime},m^{\prime}}} \\{\theta \cdot v_{l^{''}m^{''}}} \\{\delta \cdot v_{l^{''}m^{''}}} \\{\mu \cdot v_{{l^{\prime}}^{''},{m^{\prime}}^{''}}} \\{\omega \cdot v_{{l^{\prime}}^{''},{m^{\prime}}^{''}}}\end{bmatrix}$

where the quantity v_(l,m) is a vector related to a first beam set, andthe quantity v_(l′,m′) is a vector related to a second beam set, and thequantity v_(l″,m″) is a vector related to a third beam set, and thequantity is a vector related to a fourth beam set, the parametercombination (l, m), (l′, m′), (l″, m″) and (l′″, m′″) may be regarded asindices of four different beams, respectively. For example, theparameter combination (l, m), (l′, m′), (l″, m″) and (l′″, m′″) may beselected independently.

In some embodiments, the quantities α, β, γ, θ, δ, μ, ω are variousparameters for control of the beam sets, for example, the quantities α,β, γ, θ, δ, μ, ω may be phase rotation between beam sets. In someembodiments, all of the values of parameter combination (l, m), (l′,m′), (l″, m″) and (l′″, m′″) should be reported from a terminal deviceto a network device. For example, the values can be jointly encoded orseparately encoded. In some embodiments, for the single codebook, theremay be four configurations of codebook subset restriction (CBSR). Forexample, the first CBSR is used for restriction of (l, m), the secondCBSR is used for restriction of (l′, m′), the third CBSR is used forrestriction of (l″, m″), and the fourth CBSR is used for restriction of(l′″, m′″).

In some embodiments, the quantities β and/or θ and/or μ are the phasedifference between different panels/TRPs. In some embodiments, thenumber of available values for the quantities β and/or θ and/or μ may beconfigurable. In some embodiments, for the first configuration, thenumber of available values for the quantities β and/or θ and/or μ may be4. For example, the values may be QPSK, or any of {1, j, −1, −j}. Andfor the second configuration, the number of available values for thequantities β and/or θ and/or μ may be 8. For example, the values may be8 PSK, or any of {e^(j*2π*0/8), e^(j*2π*1/8), e^(j*2π*2/8),e^(j*2π*3/8), e^(j*2π*4/8), e^(j*2π*5/8), e^(j*2π*6/8), e^(j*2π*7/8)}.In some embodiments, there may be a third configuration, and the numberof available values for the quantities β and/or θ and/or μ may be 2. Forexample, the values may be BPSK, or any of {1,j} or any of {1, −1}.

In some embodiments, for multi-TRP transmission, the number of panelsfor transmission to a given terminal device from the different TRPsshould be same. In some embodiments, for a column of the multi-TRP/panelcodebook, the number of quantities including v_(l,m), is same with thenumber of quantities including v_(l′,m′). In some embodiments, for acolumn of the multi-TRP/panel codebook, the number of quantitiesincluding v_(l,m) is same with the number of quantities includingv_(l′,m′), and same with the number of quantities including v_(l″,m″),and same with the number of quantities including v_(l′″,m′″). In oneembodiment, the number of panels for multi-TRP codebook can only be onefor each TRP. For example, for a column of the multi-TRP/panel codebook,the number of quantities including v_(l,m) is two and the number ofquantities including v_(l′,m′) is two.

In some embodiments, in the example scenario as depicted in FIG. 1, acolumn of the proposed multi-TRP codebook for the network devices 110,120 may be written as below.

$W_{l,m,l^{\prime},m^{\prime},p,n} = \begin{bmatrix}v_{l,m} \\{\varphi_{n\; 0}v_{l,m}} \\{a_{p\; 1}b_{n\; 1}v_{l^{\prime},m^{\prime}}} \\{a_{p\; 2}b_{n\; 2}v_{l^{\prime},m^{\prime}}}\end{bmatrix}$

where the quantity v_(l,m) is a vector related to a beam set for thenetwork device 110, the quantity v_(l′,m′) is a vector related toanother beam set for the network device 120, the parameter combination(l, m) and (l′, m′) may be regarded as indices of two different beams,respectively, and the quantities φ_(n0), a_(p1), a_(p2), b_(n1), b_(n2)are various parameters for control of the beam sets. More details forthese quantities can be found in Release 15 specifications.

Different from the conventional codebook, in the column of the proposedmulti-TRP codebook, the upper two elements v_(l,m) and φ_(n0)v_(l,m)represent a beam set for one network device of the plurality of thenetwork devices, such as the network device 110, and the lower twoelements a_(p1)b_(n1) v_(l′,m′) and a_(p2)b_(p2)v_(l′,m′) representanother beam set for another network device of the plurality of thenetwork devices, such as the network device 120. In this way, theproposed multi-TRP codebook enables multi-TRP PMI feedback for aplurality of the network devices in communication of a terminal device.

In the communication environment 100, the power for CSI-RS resources fordifferent network devices (such as the network devices 110, 120) may bedifferent, and/or the path loss for different links may be different.Also, the number of panels in different network devices may bedifferent. Then, even the power for CSI-RS resource transmission fromdifferent network devices are same, the transmitted power from differentpanels may be different. For example, the network device 110 has onepanel (8 ports), and the network device 120 has two panels (total 16ports). If only one panel from each network device can be transmitted,the power from the network device 110 may be P, and the power from thenetwork device 120 may be only P/2.

In some embodiments, power parameters may be introduced for differentnetwork devices, so as to take account into the above discussed powerdifferences. In these embodiments, different beams are included in theproposed multi-TRP codebook, and the beam index reporting may bewideband. To be more specific, in order to control power of therespective beam sets for a plurality of the network devices, theelements in the column of the proposed multi-TRP codebook may include afirst element representing a reference beam set. In addition, there maybe a second element comprising a power parameter representing a ratio ofpower for a respective beam set to power for the reference beam set. Inthis way, the power differences among the plurality of network devicesmay be reduced or eliminated.

In some embodiments, a column of the multi-TRP/panel codebook may bewritten as below.

$W_{l,m,l^{\prime},m^{\prime}} = {{\begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{c \cdot \beta \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \gamma \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}\mspace{14mu}{or}\mspace{14mu} W_{l,m,l^{\prime},m^{\prime}}} = {{\begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{c \cdot \beta \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \gamma \cdot v_{l^{\prime},m^{\prime}}} \\{\theta \cdot v_{l,m}} \\{\delta \cdot v_{l,m}} \\{c \cdot \mu \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \omega \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}\mspace{14mu}{or}\mspace{14mu} W_{l,m,l^{\prime},m^{\prime}}} = \begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{\beta \cdot v_{l,m}} \\{\gamma \cdot v_{l,m}} \\{c \cdot \theta \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \delta \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \mu \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \omega \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}}}$

where the quantity v_(l,m) is a vector related to a first beam set, andthe quantity v_(l′,m′) is a vector related to a second beam set, theparameter combination (l, m) and (l′, m′) may be regarded as indices oftwo different beams, respectively. For example, the parametercombination (l, m) and (l′, m′) may be selected independently.

In some embodiments, the quantity c is a parameter for power ratio forthe second beam set. For example, the available value for c may be atleast one of {1, √{square root over (½)}, √{square root over (¼)},√{square root over (⅛)}, √{square root over ( 1/16)}, √{square root over( 1/32)}, √{square root over ( 1/64)}, 0} or at least one of {1,√{square root over (½)}, √{square root over (¼)}, 0}. In someembodiments, the quantities α, β, γ, θ, δ, μ, ω are various parametersfor control of the beam sets, for example, the quantities α, β, γ, θ, δ,μ, ω may be phase rotation between beam sets. In some embodiments, bothof the values of parameter combination (l, m) and (l′, m′) should bereported from a terminal device to a network device. For example, thevalues can be jointly encoded or separately encoded.

In some embodiments, a column of the multi-TRP/panel codebook may bewritten as below.

$W_{l,m,l^{\prime},m^{\prime},{l^{''}m^{''}},{l^{\prime}}^{''},{m^{\prime}}^{''}} = \begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{c_{1} \cdot \beta \cdot v_{l^{\prime},m^{\prime}}} \\{c_{1} \cdot \gamma \cdot v_{l^{\prime},m^{\prime}}} \\{c_{2} \cdot \theta \cdot v_{l^{''}m^{''}}} \\{c_{2} \cdot \delta \cdot v_{l^{''}m^{''}}} \\{c_{3} \cdot \mu \cdot v_{{l^{\prime}}^{''},{m^{\prime}}^{''}}} \\{c_{3} \cdot \omega \cdot v_{{l^{\prime}}^{''},{m^{\prime}}^{''}}}\end{bmatrix}$

where the quantity v_(l,m) is a vector related to a first beam set, andthe quantity v_(l′,m′) is a vector related to a second beam set, and thequantity v_(l″,m″) is a vector related to a third beam set, and thequantity v_(l′″,m′″) is a vector related to a fourth beam set, theparameter combination (l, m), (l′, m′), (l″,m″) and (l′″, m′″) may beregarded as indices of four different beams, respectively. For example,the parameter combination (l, m), (l′, m′), (l″, m″) and (l′″, m′″) maybe selected independently.

In some embodiments, the quantities c₁, c₂, c₃ are parameters for powerratio for the second beam set, the third beam set, the fourth beam set,respectively. For example, the available value for any of c₁, c₂, c₃ maybe at least one of {1, √{square root over (½)}, √{square root over (¼)},√{square root over (⅛)}, √{square root over ( 1/16)}, √{square root over( 1/32)}, √{square root over ( 1/64)}, 0} or at least one of {1,√{square root over (½)}, √{square root over (¼)}, 0}. In someembodiments, the quantities α, β, γ, θ, δ, μ, ω are various parametersfor control of the beam sets, for example, the quantities α, β, γ, θ, δ,μ, ω may be phase rotation between beam sets. In some embodiments, allof the values of parameter combination (l, m), (l, m′), (l″, m″) and(l′″, m′″) should be reported from a terminal device to a networkdevice. For example, the values can be jointly encoded or separatelyencoded.

For example, with this power parameter, a column of the proposedmulti-TRP codebook for the network devices 110, 120 may be written asbelow.

$W_{l,m,l^{\prime},m^{\prime},p,n,q} = \begin{bmatrix}v_{l,m} \\{\varphi_{n\; 0}v_{l,m}} \\{c_{q}a_{p\; 1}b_{n\; 1}v_{l^{\prime},m^{\prime}}} \\{c_{q}a_{p\; 2}b_{n\; 2}v_{l^{\prime},m^{\prime}}}\end{bmatrix}$

where the quantity v_(l,m) is a vector related to a beam set for thenetwork device 110, the quantity v_(l′,m′) is a vector related toanother beam set for the network device 120, the parameter combination(l, m) and (l′, m′) may be regarded as indices of two different beams,respectively, and the quantities φ_(n0), a_(p1), a_(p2), b_(n1), b_(n2)are various parameters for control of the beam sets. More details forthese quantities can be found in Release 15 specifications.

Analogous to the above, the upper two elements v_(l,m) and φ_(n0)v_(l,m)may represent the beam set for the network device 110, and the lower twoelements c_(q)a_(p1)b_(n1)v_(l′,m′) and c_(q)a_(p2)b_(p2)v_(l′,m′) mayrepresent another beam set for the network device 120. In addition, inthis example, the power parameter c_(q) may be included in the lower twoelements for the network device 120, which represents a ratio of thepower for the beam set for the network device 120 to the power for thebeam set for the network device 110. That is, the beam set for thenetwork device 110 is used as the reference beam set.

In some embodiments, dynamic network device selection can be supportedby the proposed multi-TRP codebook. Also, in these embodiments,different beams are included in the proposed multi-TRP codebook, and thebeam index reporting may be wideband. In order to realize the dynamicselection of the plurality of network devices, one or more element inthe column of the proposed multi-TRP codebook may comprise a controlparameter for enabling or disabling a respective one of the plurality ofnetwork devices. In this way, the terminal device 130 may readily selectthe desirable network devices to communicate with, through the proposedmulti-TRP codebook.

In some embodiments, a column of the multi-TRP/panel codebook may bewritten as below.

$W_{l,m,l^{\prime},m^{\prime}} = {{\begin{bmatrix}{d \cdot v_{l,m}} \\{d \cdot \alpha \cdot v_{l,m}} \\{c \cdot \beta \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \gamma \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}\mspace{14mu}{or}\mspace{14mu} W_{l,m,l^{\prime},m^{\prime}}} = {{\begin{bmatrix}{d \cdot v_{l,m}} \\{d \cdot \alpha \cdot v_{l,m}} \\{c \cdot \beta \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \gamma \cdot v_{l^{\prime},m^{\prime}}} \\{d \cdot \theta \cdot v_{l,m}} \\{d \cdot \delta \cdot v_{l,m}} \\{c \cdot \mu \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \omega \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}\mspace{14mu}{or}\mspace{14mu} W_{l,m,l^{\prime},m^{\prime}}} = \begin{bmatrix}{d \cdot v_{l,m}} \\{d \cdot \alpha \cdot v_{l,m}} \\{d \cdot \beta \cdot v_{l,m}} \\{d \cdot \gamma \cdot v_{l,m}} \\{c \cdot \theta \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \delta \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \mu \cdot v_{l^{\prime},m^{\prime}}} \\{c \cdot \omega \cdot v_{l^{\prime},m^{\prime}}}\end{bmatrix}}}$

where the quantity v_(l,m) is a vector related to a first beam set, andthe quantity v_(l′,m′) is a vector related to a second beam set, theparameter combination (l, m) and (l′, m′) may be regarded as indices oftwo different beams, respectively. For example, the parametercombination (l, m) and (l′, m′) may be selected independently.

In some embodiments, the quantity d is a parameter for power indicationfor the first beam set. For example, the available value for d may be atleast one of {1, √{square root over (½)}, √{square root over (¼)},√{square root over (⅛)}, √{square root over ( 1/16)}, √{square root over( 1/32)}, √{square root over ( 1/64)}, 0} or at least one of {1,√{square root over (½)}, √{square root over (¼)}, 0}. In someembodiments, the quantity c is a parameter for power ratio for thesecond beam set. For example, the available value for c may be at leastone of {1, √{square root over (½)}, √{square root over (¼)}, √{squareroot over (⅛)}, √{square root over ( 1/16)}, √{square root over (1/32)}, √{square root over ( 1/64)}, 0} or at least one of {1, √{squareroot over (½)}, √{square root over (¼)}, 0}.

In some embodiments, the number of available values for the quantity dmay be different from the number of available values for the quantity c.For example, the number of available values for the quantity d may beless than the number of values for the quantity c. In some embodiments,at least one of the values for quantity c may be different from any ofthe available value for quantity d. In some embodiments, the number ofvalues and/or the value for the quantity c may be dependent on differentvalues of quantity d.

In some embodiments, the available values for d may be at least one of{0, 1} or at least one of {1, √{square root over (½)}, √{square rootover (¼)}, 0}. In some embodiments, when the value for quantity d is 0,the number of values for quantity c is only 1. In some embodiments, whenthe value for quantity d is 0, the available value for quantity c is 1.In some embodiments, when the value for quantity d is not 0, forexample, the value for quantity for d is 1, the number of values forquantity c is larger than 1, for example, 2 or 4 or 8. In someembodiments, when the value for quantity d is not 0, for example, thevalue for quantity for d is 1, the available value for quantity c is atleast one of {1, √{square root over (½)}, √{square root over (¼)},√{square root over (⅛)}, √{square root over ( 1/16)}, √{square root over( 1/32)}, √{square root over ( 1/64)}, 0} or at least one of {1,√{square root over (½)}, √{square root over (¼)}, 0}.

In some embodiments, the quantities α, β, γ, θ, δ, μ, ω are variousparameters for control of the beam sets, for example, the quantities α,β, γ, θ, δ, μ, ω may be phase rotation between beam sets. In someembodiments, both of the values of parameter combination (l, m) and (l′,m′) should be reported from a terminal device to a network device. Forexample, the values can be jointly encoded or separately encoded.

In some embodiments, the value of quantity d for the power indicator ofthe first beam, and the value of quantity c for the power ratio of thesecond beam should be reported from a terminal device to a networkdevice. For example, the values can be jointly encoded or separatelyencoded. In some embodiments, the number of bits for reporting of thequantity d may be different from the number of bits for reporting ofquantity c. For example, the number of bits for reporting of quantity dmay be less than the number of bits for reporting of quantity c. Forexample, the number of bits for reporting the quantity d may be 1. Foranother example, the number of bits for reporting the quantity c may be2 or 3 or 4.

In some embodiments, the number of bits for reporting of the quantity cmay be dependent on the reported value of quantity d. In someembodiments, the number of bits for reporting of the quantity c may bedifferent for different reported values of quantity d. In oneembodiment, if the reported value of quantity d is 0, there may be noneed of reporting the quantity c. In another embodiment, if the reportedvalue of quantity d is not 0, for example, the reported value ofquantity d is 1, the number of bits for reporting of quantity c may be 2or 3 or 4.

In some embodiments, a column of the multi-TRP/panel codebook may bewritten as below.

$W_{l,m,l^{\prime},m^{\prime},{l^{''}m^{''}},{l^{\prime}}^{''},{m^{\prime}}^{''}} = \begin{bmatrix}v_{l,m} \\{\alpha \cdot v_{l,m}} \\{c_{1} \cdot \beta \cdot v_{l^{\prime},m^{\prime}}} \\{c_{1} \cdot \gamma \cdot v_{l^{\prime},m^{\prime}}} \\{c_{2} \cdot \theta \cdot v_{l^{''}m^{''}}} \\{c_{2} \cdot \delta \cdot v_{l^{''}m^{''}}} \\{c_{3} \cdot \mu \cdot v_{{l^{\prime}}^{''},{m^{\prime}}^{''}}} \\{c_{3} \cdot \omega \cdot v_{{l^{\prime}}^{''},{m^{\prime}}^{''}}}\end{bmatrix}$

where the quantity v_(l,m) is a vector related to a first beam set, andthe quantity v_(l′,m′) is a vector related to a second beam set, and thequantity is a vector related to a third beam set, and the quantityv_(l′″,m′″) is a vector related to a fourth beam set, the parametercombination (l, m), (l′, m′), (l″, m″) and (l′″, m′″) may be regarded asindices of four different beams, respectively. For example, theparameter combination (l, m), (l′, m′), (l″, m″) and (l′″, m′″) may beselected independently.

In some embodiments, the quantity d is a parameter for power indicationfor the first beam set. For example, the available value for d may be atleast one of {1, √{square root over (½)}, √{square root over (¼)},√{square root over (⅛)}, √{square root over ( 1/16)}, √{square root over( 1/32)}, √{square root over ( 1/64)}, 0} or at least one of {1,√{square root over (½)}, √{square root over (¼)}, 0}. In someembodiments, the quantities c₁, c₂, c₃ are parameters for power ratiofor the second beam set, the third beam set, the fourth beam set,respectively. For example, the available value for any of c₁, c₂, c₃ maybe at least one of {1, √{square root over (½)}, √{square root over (¼)},√{square root over (⅛)}, √{square root over ( 1/16)}, √{square root over( 1/32)}, √{square root over ( 1/64)}, 0} or at least one of {1,√{square root over (½)}, √{square root over (¼)}, 0}.

In some embodiments, the quantities α, β, γ, θ, δ, μ, ω are variousparameters for control of the beam sets, for example, the quantities α,β, γ, θ, δ, μ, ω may be phase rotation between beam sets. In someembodiments, all of the values of parameter combination (l, m), (l′,m′), (l″, m″) and (l′″, m′″) should be reported from a terminal deviceto a network device. For example, the values can be jointly encoded orseparately encoded.

In some embodiments, the number of available values for the quantity dmay be different from the number of available values for each of thequantities c₁, c₂, c₃. For example, the number of available values forthe quantity d may be less than the number of values for each of thequantities c₁, c₂, c₃. In some embodiments, at least one of the valuesfor each of the quantities c₁, c₂, c₃ may be different from any of theavailable value for quantity d. In some embodiments, the number ofvalues and/or the value for each of the quantities c₁, c₂, c₃ may bedependent on different values of quantity d.

In some embodiments, the available values for d may be at least one of{0, 1} or at least one of {1, √{square root over (½)}, √{square rootover (¼)}, 0}. In some embodiments, when the value for quantity d is 0,the number of values for each of the quantities c₁, c₂, c₃ is only 1. Insome embodiments, when the value for quantity d is 0, the availablevalue for any of the quantities c₁, c₂, c₃ is 1. In some embodiments,when the value for quantity d is not 0, for example, the value forquantity for d is 1, the number of values for each of the quantities c₁,c₂, c₃ is larger than 1, for example, 2 or 4 or 8. In some embodiments,when the value for quantity d is not 0, for example, the value forquantity for d is 1, the available value for each of the quantities c₁,c₂, c₃ is at least one of {1, √{square root over (½)}, √{square rootover (¼)}, √{square root over (⅛)}, √{square root over ( 1/16)},√{square root over ( 1/32)}, √{square root over ( 1/64)}, 0} or at leastone of {1, √{square root over (½)}, √{square root over (¼)}, 0}.

In some embodiments, the value of quantity d for the power indicator ofthe first beam, and the values of each of the quantities c₁, c₂, c₃ forthe power ratio of the second beam should be reported from a terminaldevice to a network device. For example, the values can be jointlyencoded or separately encoded. In some embodiments, the number of bitsfor reporting of the quantity d may be different from the number of bitsfor reporting of each of the quantities c₁, c₂, c₃. For example, thenumber of bits for reporting of quantity d may be less than the numberof bits for reporting of each of the quantities c₁, c₂, c₃. For example,the number of bits for reporting the quantity d may be 1. For anotherexample, the number of bits for reporting each of the quantities c₁, c₂,c₃ may be 2 or 3 or 4.

In some embodiments, the number of bits for reporting of each of thequantities c₁, c₂, c₃ c may be dependent on the reported value ofquantity d. In some embodiments, the number of bits for reporting ofeach of the quantities c₁, c₂, c₃ may be different for differentreported values of quantity d. In one embodiment, if the reported valueof quantity d is 0, there may be no need of reporting any of thequantities c₁, c₂, c₃. In another embodiment, if the reported value ofquantity d is not 0, for example, the reported value of quantity d is 1,the number of bits for reporting of each of the quantities c₁, c₂, c₃may be 2 or 3 or 4.

For example, with this control parameter, a column of the proposedmulti-TRP codebook for the network devices 110, 120 may be written asbelow.

$W_{l,m,l^{\prime},m^{\prime},p,n,q} = \begin{bmatrix}{d_{q}v_{l,m}} \\{d_{q}\varphi_{n\; 0}v_{l,m}} \\{a_{p\; 1}b_{n\; 1}v_{l^{\prime},m^{\prime}}} \\{a_{p\; 2}b_{n\; 2}v_{l^{\prime},m^{\prime}}}\end{bmatrix}$

where the quantity v_(l,m) is a vector related to a beam set for thenetwork device 110, the quantity v_(l′,m′) is a vector related toanother beam set for the network device 120, the parameter combination(l, m) and (l′, m′) may be regarded as indices of two different beams,respectively, and the quantities φ_(n0), a_(p1), a_(p2), b_(n1), b_(n2)are various parameters for control of the beam sets. More details forthese quantities can be found in Release 15 specifications.

Analogous to the above, the upper two elements d_(q) v_(l,m) andd_(q)φ_(n0)v_(l,m) may represent the beam set for the network device110, and the lower two elements a_(p1)b_(n1)v_(l′,m′) anda_(p2)b_(p2)v_(l′,m′) may represent another beam set for the networkdevice 120. In addition, in this example, the power parameter d_(q) maybe included in the upper two elements for the network device 110, whichenables or disables the network device 110. For example, when d_(q)=1,the network device 110 is enabled by the terminal device 130 for thecommunication with the terminal device 130, whereas when d_(q)=0, thenetwork device 110 is disabled by the terminal device 130 for thecommunication with the terminal device 130. The control parameter d_(q)may also be included for other network devices.

In some embodiments, the power parameters for different network devicesand the dynamic network device selection may be combined. In otherwords, the above discussed power parameter c_(q) and the controlparameter d_(q) may both be included in the proposed multi-TRP codebook.For example, a column of the proposed multi-TRP codebook for the networkdevices 110, 120, including both c_(q) and d_(q), may be written asbelow.

$W_{l,m,l^{\prime},m^{\prime},p,n,q} = \begin{bmatrix}{d_{q}v_{l,m}} \\{d_{q}\varphi_{n\; 0}v_{l,m}} \\{c_{q}a_{p\; 1}b_{n\; 1}v_{l^{\prime},m^{\prime}}} \\{c_{q}a_{p\; 2}b_{n\; 2}v_{l^{\prime},m^{\prime}}}\end{bmatrix}$

where the quantity v_(l,m) is a vector related to a beam set for thenetwork device 110, the quantity v_(l′,m′) is a vector related toanother beam set for the network device 120, the parameter combination(l, m) and (l′, m′) may be regarded as indices of two different beams,respectively, and the quantities φ_(n0), a_(p1), a_(p2), b_(n1), b_(n2)are various parameters for control of the beam sets. More details forthese quantities can be found in Release 15 specifications.

In some embodiments, the control parameter d_(q) can be 0 or 1. Ifd_(q)=1, that means the network device with associated CSI-RS isselected, and the power parameter c_(q) can be selected from the set of{1, √{square root over (½)}, √{square root over (¼)}, √{square root over(⅛)}, √{square root over ( 1/16)}, √{square root over ( 1/32)}, √{squareroot over ( 1/64)}, 0} or {1, √{square root over (½)}, √{square rootover (¼)}, 0} or {0,1}, and when c_(q)=0, that means the network devicewith associated CSI-RS is not selected. If d_(q)=0, that means thenetwork device with associated CSI-RS is not selected, and c_(q) canonly be 1.

In some cases, it is desirable for the network devices 110, 120 and theterminal device 130 to use different codebook sizes for differentcommunication scenarios. A convenient way to support different codebooksizes is to use a large codebook with many elements by default and applya codebook subset restriction in the scenarios where a smaller codebookis beneficial. With the codebook subset restriction, a subset of theprecoding matrices in the codebook is restricted so that the terminaldevice 130 has a smaller set of possible precoding matrices to choosefrom. This effectively reduces the size of the codebook, implying thatthe search for the best PMI can be done on the smaller unrestricted setof precoding matrices, thereby also reducing computational requirementsfor the terminal device 130 for this particular search.

Typically, any or both of the network devices 110, 120 would signal thecodebook subset restriction to the terminal device 130 by means of abitmap, one bit for each precoding matrix in the codebook, where a 1would indicate that the precoding matrix is restricted (meaning that theterminal device 130 is not allowed to choose and report said precodingmatrix). Thus, for a codebook with N elements, a bitmap of length Nwould be used to signal the codebook subset restriction. This allows forfull flexibility for the network devices 110, 120 to restrict everypossible subset of the codebook.

For the proposed multi-TRP codebook, since the elements in a column ofthe codebook represent respective beam sets for the plurality of networkdevices in communication with the terminal device 130, a plurality ofsets of codebook subset restrictions may be provided for a singlecodebook, namely, for different network devices within the proposedmulti-TRP codebook. That is, for multi-TRP transmission, the beams fromdifferent network devices are different, so a plurality of sets ofcodebook subset restrictions may be configured for the proposedmulti-TRP codebook.

In this event, for the example scenario as depicted in FIG. 1, whenselecting the precoding matrix from the proposed multi-TRP codebook, theterminal device 130 may exclude a first beam subset from the beam setfor the network device 110, and also exclude a second beam subset fromthe beam set for the network device 120. In some embodiments, the firstbeam subset may be different from the second beam subset. In otherembodiments, the first and second beam subsets may be the same. In thisway, different codebook subset restrictions may be applied to respectivebeam sets for different network devices according to their respectivecommunication properties.

In some embodiments, one or more beam combinations may be limited forthe plurality of the network devices in communication with the terminaldevice 130, such as for the network device 110, 120. That is, some beamcombinations may not be supported for the plurality of the networkdevices. For example, combination of multiple sets of codebook subsetrestrictions may be configured for the plurality of the network devices.In this event, when selecting the precoding matrix from the proposedmulti-TRP codebook, the terminal device 130 may exclude a predeterminedbeam combination of respective beams for the plurality of networkdevices, such as the network devices 110, 120.

Alternatively or additionally, report of beam indices may be based oncombination of the plurality of network devices. In addition, the bitfield can be based on the codebook subset restriction. For example, if acodebook subset restriction is applied for one beam set, only one orseveral offset values relative to the codebook subset restriction may beapplied for another beam set. In this way, the resources fortransmitting the codebook subset restrictions may be reduced.

In other embodiments, a restricted beam combination may be determined bydetermining a first beam index from a first beam set for one networkdevice, and determining other beam indices for other network devicesbased on one or several offset values. For example, for the examplescenario as depicted in FIG. 1, if the beam with an index1 is restrictedfor the network device 110, the beam with an index of index1+offset isrestricted for the network device 120.

In this event, when selecting the precoding matrix from the proposedmulti-TRP codebook, the terminal device 130 may exclude a first beamindex for a first network device of the plurality of network devices,and also exclude a second beam index for a second network device of theplurality of network devices, based on the first beam index and anoffset between the first beam index and the second beam index. In thisway, the resources for transmitting the codebook subset restrictions mayalso be reduced.

In some embodiments, for selecting the precoding matrix from theproposed multi-TRP codebook, the terminal device 130 may first determinea group of beams for a network device of the plurality of networkdevices (for example, the network device 110), and then combine aplurality of beams in the group of beams to form a combined beam for thenetwork device. In other words, the final beam for the network device110 is a combined beam of at least two beams in the beam group. In thisway, a combined beam with advantages from a plurality of beams may beobtained for a network device.

In some embodiments, only 2 layers may be supported in this type IIcodebook for multi-TRP, and two sets of beams (each set with 2 beams)may be selected. The two beams are combined within each set. It is to beunderstood that the particular number of layers is only an example, andany other suitable number of layers may be supported in otherembodiments,

At block 230, the terminal device 130 transmits an index of theprecoding matrix (PMI) to at least one of the plurality of networkdevices. For example, in the example scenario as depicted in FIG. 1, theterminal device 130 may transmits the PMI to either or both of thenetwork device 110, 120. If the network device 110, 120 are twogNBs/TRPs and the PMI is transmitted to the network device 110, the PMImay be transmitted from the network device 110 to the network device 120via the communication link between them.

In some embodiments, the reporting of the precoding matrix indexincluding a plurality of beam indices for a plurality of network devicesis wideband. In other embodiments, the reporting may also be narrowband.In some embodiments, 4 ports, 8 ports, 16 ports and 32 ports may besupported by the proposed multi-TRP codebook. It is understood thatthese particular numbers of ports are only examples, and any othersuitable number of the ports may be supported in other embodiments.

In some embodiments, a beam index for one network device of theplurality of network devices is reported, and another beam index foranother network device of the plurality of network device may be basedon an offset between the two beam indices. For example, the terminaldevice 130 may transmit a first beam index for the network device 110,and also transmit an offset between the first beam index and a secondbeam index for the network device 120. In this way, the resources forreporting the precoding matrix index may be reduced.

In some embodiments, the reporting of the precoding matrix index may bedivided into two steps. In a first step, a beam group is reported forthe plurality of network devices. In a second step, beam indices fromthe beam group are reported, and the beam indices are one to one for theplurality of network devices. For example, the terminal device 130 maytransmit a group index of a group of beams for both the network devices110, 120, and also transmit respective beam indices of the group ofbeams for the network devices 110, 120. In this way, the resources forreporting the precoding matrix index may be also reduced.

FIG. 3 is a simplified block diagram of a device 300 that is suitablefor implementing embodiments of the present disclosure. The device 300can be considered as a further example embodiment of the terminal device130 as shown in FIG. 1. Accordingly, the device 300 can be implementedat or as at least a part of the terminal device 130.

As shown, the device 300 includes a processor 310, a memory 320 coupledto the processor 310, a suitable transmitter (TX) and receiver (RX) 340coupled to the processor 310, and a communication interface coupled tothe TX/RX 340. The memory 320 stores at least a part of a program 330.The TX/RX 340 is for bidirectional communications. The TX/RX 340 has atleast one antenna to facilitate communication, though in practice anAccess Node mentioned in this application may have several ones. Thecommunication interface may represent any interface that is necessaryfor communication with other network elements, such as X2 interface forbidirectional communications between eNBs, S1 interface forcommunication between a Mobility Management Entity (MME)/Serving Gateway(S-GW) and the eNB, Un interface for communication between the eNB and arelay node (RN), or Uu interface for communication between the eNB and aterminal device.

The program 330 is assumed to include program instructions that, whenexecuted by the associated processor 310, enable the device 300 tooperate in accordance with the embodiments of the present disclosure, asdiscussed herein with reference to FIG. 2. The embodiments herein may beimplemented by computer software executable by the processor 310 of thedevice 300, or by hardware, or by a combination of software andhardware. The processor 310 may be configured to implement variousembodiments of the present disclosure. Furthermore, a combination of theprocessor 310 and memory 320 may form processing means 350 adapted toimplement various embodiments of the present disclosure.

The memory 320 may be of any type suitable to the local technicalnetwork and may be implemented using any suitable data storagetechnology, such as a non-transitory computer readable storage medium,semiconductor based memory devices, magnetic memory devices and systems,optical memory devices and systems, fixed memory and removable memory,as non-limiting examples. While only one memory 320 is shown in thedevice 300, there may be several physically distinct memory modules inthe device 300. The processor 310 may be of any type suitable to thelocal technical network, and may include one or more of general purposecomputers, special purpose computers, microprocessors, digital signalprocessors (DSPs) and processors based on multicore processorarchitecture, as non-limiting examples. The device 300 may have multipleprocessors, such as an application specific integrated circuit chip thatis slaved in time to a clock which synchronizes the main processor.

The components included in the apparatuses and/or devices of the presentdisclosure may be implemented in various manners, including software,hardware, firmware, or any combination thereof. In one embodiment, oneor more units may be implemented using software and/or firmware, forexample, machine-executable instructions stored on the storage medium.In addition to or instead of machine-executable instructions, parts orall of the units in the apparatuses and/or devices may be implemented,at least in part, by one or more hardware logic components. For example,and without limitation, illustrative types of hardware logic componentsthat can be used include Field-programmable Gate Arrays (FPGAs),Application-specific Integrated Circuits (ASICs), Application-specificStandard Products (ASSPs), System-on-a-chip systems (SOCs), ComplexProgrammable Logic Devices (CPLDs), and the like.

Generally, various embodiments of the present disclosure may beimplemented in hardware or special purpose circuits, software, logic orany combination thereof. Some aspects may be implemented in hardware,while other aspects may be implemented in firmware or software which maybe executed by a controller, microprocessor or other computing device.While various aspects of embodiments of the present disclosure areillustrated and described as block diagrams, flowcharts, or using someother pictorial representation, it will be appreciated that the blocks,apparatus, systems, techniques or methods described herein may beimplemented in, as non-limiting examples, hardware, software, firmware,special purpose circuits or logic, general purpose hardware orcontroller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer programproduct tangibly stored on a non-transitory computer readable storagemedium. The computer program product includes computer-executableinstructions, such as those included in program modules, being executedin a device on a target real or virtual processor, to carry out theprocess or method as described above with reference to any of FIGS. 3and 4. Generally, program modules include routines, programs, libraries,objects, classes, components, data structures, or the like that performparticular tasks or implement particular abstract data types. Thefunctionality of the program modules may be combined or split betweenprogram modules as desired in various embodiments. Machine-executableinstructions for program modules may be executed within a local ordistributed device. In a distributed device, program modules may belocated in both local and remote storage media.

Program code for carrying out methods of the present disclosure may bewritten in any combination of one or more programming languages. Theseprogram codes may be provided to a processor or controller of a generalpurpose computer, special purpose computer, or other programmable dataprocessing apparatus, such that the program codes, when executed by theprocessor or controller, cause the functions/operations specified in theflowcharts and/or block diagrams to be implemented. The program code mayexecute entirely on a machine, partly on the machine, as a stand-alonesoftware package, partly on the machine and partly on a remote machineor entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium,which may be any tangible medium that may contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device. The machine readable medium may be a machinereadable signal medium or a machine readable storage medium. A machinereadable medium may include but not limited to an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatus,or device, or any suitable combination of the foregoing. More specificexamples of the machine readable storage medium would include anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing.

Further, while operations are depicted in a particular order, thisshould not be understood as requiring that such operations be performedin the particular order shown or in sequential order, or that allillustrated operations be performed, to achieve desirable results. Incertain circumstances, multitasking and parallel processing may beadvantageous. Likewise, while several specific embodiment details arecontained in the above discussions, these should not be construed aslimitations on the scope of the present disclosure, but rather asdescriptions of features that may be specific to particular embodiments.Certain features that are described in the context of separateembodiments may also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment may also be implemented in multipleembodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specificto structural features and/or methodological acts, it is to beunderstood that the present disclosure defined in the appended claims isnot necessarily limited to the specific features or acts describedabove. Rather, the specific features and acts described above aredisclosed as example forms of implementing the claims.

1. A method for communication, comprising: measuring downlink channelconditions related to a plurality of network devices in communicationwith a terminal device; selecting a precoding matrix from a codebookbased on the downlink channel conditions, elements in a column of thecodebook representing respective beam sets for the plurality of networkdevices, the precoding matrix indicating respective beams for theplurality of network devices; and transmitting an index of the precodingmatrix to at least one of the plurality of network devices.
 2. Themethod of claim 1, wherein transmitting the index of the precodingmatrix comprises: transmitting a first beam index for a first networkdevice of the plurality of network devices; and transmitting an offsetbetween the first beam index and a second beam index for a secondnetwork device of the plurality of network devices.
 3. The method ofclaim 1, wherein transmitting the index of the precoding matrixcomprises: transmitting a group index of a group of beams; andtransmitting beam indices of the group of beams for the plurality ofnetwork devices.
 4. The method of claim 1, wherein the elements in thecolumn of the codebook comprise: a first element representing areference beam set, and a second element comprising a power parameterrepresenting a ratio of power for a respective beam set to power for thereference beam set.
 5. The method of claim 1, wherein at least one ofthe elements in the column of the codebook comprises a control parameterfor enabling or disabling a respective one of the plurality of networkdevices.
 6. The method of claim 1, wherein selecting the precodingmatrix comprises: excluding a first beam subset from a first beam set ofthe respective beam sets for the plurality of network devices; andexcluding a second beam subset from a second beam set of the respectivebeam sets for the plurality of network devices.
 7. The method of claim1, wherein selecting the precoding matrix comprises: excluding apredetermined beam combination of respective beams for the plurality ofnetwork devices.
 8. The method of claim 1, wherein selecting theprecoding matrix comprises: excluding a first beam index for a firstnetwork device of the plurality of network devices; and excluding asecond beam index for a second network device of the plurality ofnetwork devices, based on the first beam index and an offset between thefirst beam index and the second beam index.
 9. The method of claim 1,wherein selecting the precoding matrix comprises: determining a group ofbeams for a network device of the plurality of network devices; andcombining a plurality of beams in the group of beams to form a combinedbeam for the network device.
 10. A terminal device, comprising: aprocessor; and a memory storing instructions, the memory and theinstructions being configured, with the processor, to cause the terminaldevice to: measure downlink channel conditions related to a plurality ofnetwork devices in communication with a terminal device; select aprecoding matrix from a codebook based on the downlink channelconditions, elements in a column of the codebook representing respectivebeam sets for the plurality of network devices, the precoding matrixindicating respective beams for the plurality of network devices; andtransmit an index of the precoding matrix to at least one of theplurality of network devices.
 11. The terminal device of claim 10,wherein the memory and the instructions are further configured, with theprocessor, to cause the terminal device to: transmit a first beam indexfor a first network device of the plurality of network devices; andtransmit an offset between the first beam index and a second beam indexfor a second network device of the plurality of network devices.
 12. Theterminal device of claim 10, wherein the memory and the instructions arefurther configured, with the processor, to cause the terminal device to:transmit a group index of a group of beams; and transmit beam indices ofthe group of beams for the plurality of network devices.
 13. Theterminal device of claim 10, wherein the elements in the column of thecodebook comprise: a first element representing a reference beam set,and a second element comprising a power parameter representing a ratioof power for a respective beam set to power for the reference beam set.14. The terminal device of claim 10, wherein at least one of theelements in the column of the codebook comprises a control parameter forenabling or disabling a respective one of the plurality of networkdevices.
 15. The terminal device of claim 10, wherein the memory and theinstructions are further configured, with the processor, to cause theterminal device to: exclude a first beam subset from a first beam set ofthe respective beam sets for the plurality of network devices; andexclude a second beam subset from a second beam set of the respectivebeam sets for the plurality of network devices.
 16. The terminal deviceof claim 10, wherein the memory and the instructions are furtherconfigured, with the processor, to cause the terminal device to: excludea predetermined beam combination of respective beams for the pluralityof network devices.
 17. The terminal device of claim 10, wherein thememory and the instructions are further configured, with the processor,to cause the terminal device to: exclude a first beam index for a firstnetwork device of the plurality of network devices; and exclude a secondbeam index for a second network device of the plurality of networkdevices, based on the first beam index and an offset between the firstbeam index and the second beam index.
 18. The terminal device of claim10, wherein the memory and the instructions are further configured, withthe processor, to cause the terminal device to: determine a group ofbeams for a network device of the plurality of network devices; andcombine a plurality of beams in the group of beams to form a combinedbeam for the network device.
 19. A computer readable medium havinginstructions stored thereon, the instructions, when executed on at leastone processor of a device, causing the device to perform act comprising:measuring downlink channel conditions related to a plurality of networkdevices in communication with a terminal device; selecting a precodingmatrix from a codebook based on the downlink channel conditions,elements in a column of the codebook representing respective beam setsfor the plurality of network devices, the precoding matrix indicatingrespective beams for the plurality of network devices; and transmittingan index of the precoding matrix to at least one of the plurality ofnetwork devices.
 20. The computer readable medium of claim 19, whereintransmitting the index of the precoding matrix comprises: transmitting afirst beam index for a first network device of the plurality of networkdevices; and transmitting an offset between the first beam index and asecond beam index for a second network device of the plurality ofnetwork devices.